1. Field of the Invention
The present invention relates to a developing apparatus and an image forming apparatus that incorporates the developing apparatus.
2. Description of the Related Art
Among conventional image forming apparatuses based on electrophotography are printers, copying machines, facsimile machines, and other multi function apparatuses. A printer performs electrophotographic processes including charging exposing, developing, transferring, cleaning and neutralizing. Through these processes, a toner image is formed on a photoconductive drum, and is transferred onto a medium such as paper. Subsequently, the toner image is fixed into a permanent image.
An electrophotographic printer incorporates a developing unit that usually uses one-component toner. A toner supplying roller formed of sponge supplies the toner to a developing roller, which in turn supplies the toner to the photoconductive drum to develop an electrostatic latent image with the toner into a toner image.
During developing process, only the toner on the developer roller that is brought into contact with the electrostatic latent image is transferred to the photoconductive drum to develop the electrostatic latent image, and the rest remains on the photoconductive drum. This may leave a reversal image of the electrostatic latent image on the developing roller.